In semiconductor processing, transistors may be formed on semiconductor wafers. The transistors may include a gate structure, a source, a drain, and a channel region and may be NMOS (N Channel Metal Oxide Semiconductor) or PMOS (P Channel Metal Oxide Semiconductor) transistors. The transistors and other devices may be interconnected to form integrated circuits (ICs). The ICs may then be packaged and sold. The performance of the ICs may depend on the performance of the transistors.